Fall 2023 Climate Outlook for northeastern South Carolina and southeastern North Carolina

September is the beginning of meeorological fall -- a transition season when lowering sun angles, shorter days, and longer nights cause temperatures to drop.  Cold fronts bringing cooler and drier air from Canada will begin to arrive as fall progresses.  High temperatures normally in the 80s throughout September fall into the mid 60s by the end of November.  Late fall is also when many locations across the eastern Carolinas will experience their first frosty morning since last winter or spring.

     How is meteorological fall different from fall on the calendar?

The NWS Climate Prediction Center is predicting a slightly increased chance for above normal temperatures across the Southeast this fall.  Their precipitation outlook shows a slightly increased potential for above normal rainfall across all of North and South Carolina.

Temperatures

Factors that may affect temperatures across the Carolinas this fall include:

• Ongoing trends toward warmer air temperatures as a consequence of Climate Change
• Sea surface temperatures running above normal across a large portion of the North Atlantic Ocean
• An intensifying El Niño in the Pacific Ocean that should have global weather impacts

Recent Climate Change is being caused by increasing atmospheric concentration of greenhouse gases from the extraction and burning of fossil fuels and the clearing of forests.  Greenhouse gases such as carbon dioxide and methane trap heat within the atmosphere that would otherwise radiate out into space.  Average temperatures across the Carolinas have increased by over 1° F since record-keeping began, somewhat less than the nearly 2° F average increase for the planet as a whole.

     Climate.gov: How have global temperatures changed?

     NC Climate Office: Climate Change in North Carolina

Also of concern are above-normal sea surface temperatures across much of the North Atlantic Ocean. (See graphic at right)  Between the Carolinas and Bermuda water temperatures are close to normal.  But near the Canadian maritime provinces and across the tropical Atlantic off the African coast sea water temperatures are as much as 2° to 5° C (3.6° to 9.0° F) above normal.  Air moving across unusually warm ocean water will remain warm itself, possibly affecting our air temperatures through the fall and into the coming winter too.

El Niño, a natural periodic warming of ocean waters across the tropical Pacific ocean, causes shifts in the weather across large portions of the planet.  Across the Carolinas, El Niño is well known for its tendency to help create wet winters.  But during the fall months El Niño's biggest local influence can be its suppression of tropical storms and hurricanes across the Atlantic Ocean. This is due to increased Atlantic wind shear that often accompanies El Niño, weakening some storms while preventing others from forming at all.

     What are El Niño and La Niña and how do they affect the weather?

Last winter the "El Niño Southern Oscillation" (ENSO) was in its cold phase known as La Niña.  La Niña transitioned to neutral ENSO conditions during the spring, then to El Niño this summer. 

Over the past 20 years there have been three times when winter La Niña conditions quickly transitioned to El Niño: 2018, 2009, and 2006.  The following table shows how local September through November temperatures compared to normal during each of these years.

Although the fall of 2018 was very warm, the same climate setup in the fall of 2006 produced cooler than normal readings.  This is admittedly a small sample but El Niño appears to have little consistent impact on our fall temperatures in the Carolinas.  Research from NOAA's Physical Sciences Laboratory also confirms that eastern North and South Carolina temperatures during the fall are not significantly affected by El Niño.

The first freezing temperatures of the fall usually reach the eastern Carolinas before Thanksgiving Day.  The average date of the first freeze ranges from October 29 in Lumberton, NC to November 21 in Georgetown, SC, but there is considerable year-to-year variability.  This first freeze thankfully brings an end to mosquitoes, but also to summer gardens as tomatoes, peppers, and other annual plants are killed.

In Wilmington, the season's first freeze has occurred as early as October 16 (in 1878) and as late as December 29 (in 1918).  But in Southport, NC first freeze dates have been even more extreme: the 1945 growing season didn't end in Southport until temperatures finally fell to freezing on January 10, 1946!  That growing season of 327 days is the longest on record for any local city.

Rainfall & Tropical Cyclones

Fall in the Carolinas is associated with tremendous rainfall variability from year to year.  This is mainly due to the uneven distribution of Atlantic tropical storms and hurricanes. 

In fall seasons without a landfalling tropical cyclone across the Carolinas, it's tough for seasonal rainfall totals to reach the long term average regardless of whether we have La Niña, neutral, or El Niño conditions in place.  These quiet fall seasons sometimes see September through November rainfall totals less than 10 inches accompanied by developing drought conditions.

El Niño tends to create less active hurricane seasons compared to either neutral or La Niña years - however, exceptionally high water temperatures observed across most of the Atlantic Ocean this fall could offset El Niño's typical influence.  This is why NOAA's seasonal hurricane outlook continues to show an above average number of storms.

The Climate Prediction Center is calling for "equal chances" for below, near, or above normal precipitation throughout the month of September.  However for the fall season through November their outlook is for an increased potential for above normal precipitation.  This implies the risk for larger rainfall totals may be from El Niño-enhanced rainfall events developing later in the year beyond September.

The following table shows how rainfall totals compared to normal during each of the fall seasons over the past 20 years when a winter La Niña quickly transitioned to El Niño.

The Climate Prediction Center updated its seasonal hurricane outlook in August to increase the overall number of storms to 14 to 21, and to increase the odds to 60 percent that this hurricane season will see above normal activity.  The Atlantic Hurricane Season runs through November 30.

Across the eastern Carolinas fall is typically the most active portion of the hurricane season.  Since 1870 when weather records began in Wilmington, over half (57 percent) of all tropical cyclones which produced measured tropical storm force (39 mph) or greater gusts have occurred in September or October.

Preparedness for hurricanes starts now.  NOAA maintains a curated list of resources for help get you and your family ready: https://www.noaa.gov/hurricane-prep

Fall Beach Hazards

Tropical storms and hurricanes can have impacts on the beaches of North and South Carolina even when the storms are located thousands of miles away.  Long-period swells generated by hurricanes travel great distances across the ocean and can create large surf and dangerous rip currents when they reach the beaches.  Since 2004 when the National Weather Service in Wilmington began collecting daily surf reports from lifeguards, September has been the most active month for "moderate" or "strong" rip current reports -- often the result of waves generated by hurricanes well offshore.

     NOAA/USLA Rip Current Safety Toolkit

Ocean water temperatures will cool over the next few months due to longer nights and cooler air temperatures.  Temperatures in the surf typically fall into the 70s by the beginning of October, and into the 60s by the beginning of November.

If your plans include spending time in the water this fall, first check our beach forecasts which include surf height, temperatures, lightning risk, rip current risk, and more.

Coastal Flooding Potential

There are several periods this fall when astronomical tides will be large enough to cause concern for coastal flooding at our local beaches and along tidal creeks and rivers.  "Sunny day" flood events occur when strong winds or storms are not necessary to create minor coastal flooding due to tides high enough by themselves.  Specific dates when this type of flooding could occur include:

• September 26 to October 2
• October 27 to 31
• November 26 to 27

Tides will be particularly high during September's Full Moon (September 29) and during October's Full Moon (October 28.)  These full moons are within 2-3 days of the Moon's monthly perigee -- its closest approach in its orbit to Earth when the Moon's tidal influence is strongest.

Landfalling tropical storms or hurricanes can produce coastal flooding regardless of the astronomical tides.  And as we move into November, non-tropical storms called Nor'easters can produce strong winds and coastal flooding too.

River Flooding Potential

Rainfall totals this summer were near normal to slightly above normal for most locations across the eastern Carolinas.  Although some spots became abnormally dry for brief periods during June and August, at no point did drought conditions develop across southeastern North Carolina or northeastern South Carolina. 

Conditional river simulations from the NWS Southeast River Forecast Center (SERFC) show the chances for river flooding this fall are near normal to slightly below normal.  Rainfall from Tropical Storm Idalia back in August will keep water levels high along the Waccamaw River through the middle portion of September.

Conditional river simulations and other current and forecast river information are available for a number of points along local rivers:

Waccamaw River

• Conway, SC

Lumber River

• Lumberton, NC

Cape Fear & Northeast Cape Fear Rivers

• William O. Huske Lock & Dam
• Lock & Dam 1
• Burgaw, NC

Black Creek & Pee Dee River

• Quinby, SC
• Cheraw, SC
• Pee Dee, SC

Lynches River

• Effingham, SC

Black River

• Kingstree, SC

Additional Reading

NOAA Hurricane Season Outlook August 2023 Update:  https://www.cpc.ncep.noaa.gov/products/outlooks/hurricane.shtml

CPC: ENSO Recent Evolution, Current Status and Predictions

National Ocean Service High Tide Flooding Outlook: https://tidesandcurrents.noaa.gov/high-tide-flooding/monthly-outlook.html

NWS Wilmington Tropics Main Page:  https://www.weather.gov/ilm/tropical

NWS Wilmington Significant Local Events Archive:  https://www.weather.gov/ilm/SignificantLocalEvents

Daily Climate Normals and Records for Wilmington, Florence, North Myrtle Beach, and Lumberton. 

Research and Author: Tim Armstrong
Last Updated: September 7, 2023